1. Field of the Invention
The present invention relates to a wire-cut, electric discharge machine which is capable of positioning an end of a broken wire at a predetermined position.
2. Description of the Prior Art
In a wire-cut, electric discharge machine, a pulse-like voltage is applied between a wire installed on the wire running system and a workpiece to produce a discharge therebetween, by which the workpiece is cut into an arbitrary shape. During cutting, the wire may be broken in the workpiece unless the cutting conditions i.e., the tension of the wire, the wire take-up speed and so forth are appropriate. In the case of breakage of the wire, it is general practice in the prior art to re-install the wire by manual operation but this is very troublesome and reduces the efficiency of the cutting operation. To avoid this, there is a strong demand for automating the re-installation of the wire.
In the case of cutting a workpiece to form therein a plurality of independent configurations in succession, the prior art employs automatic operations for cutting off a wire after completion of one configuration, feeding the wire to the next cutting position and reinstalling the wire on the running system. In this case, since the wire is cut off at a predetermined position, it can automatically be reinstalled. But, in the case of breakage of the wire during cutting the position of the broken end of the wire is unknown and, accordingly, it is difficult to automate the reinstallation of the wire.